Typically, it is necessary to control the transmission of fluids in industrial processes, such as oil and gas pipeline distribution systems, chemical processing plants, etc. In some process control systems, process fluid control devices, such as butterfly valves, provide a means to control the transmission of the fluids and, in particular, may provide shut-off capabilities in a forward fluid flow direction and a reverse fluid flow direction. Although many process fluid control devices provide shut-off capabilities in both forward and reverse flow directions, these process fluid control devices may not provide the same degree of shut-off in both flow directions. For example, a butterfly valve may provide shut-off capabilities for up to a 300 psi pressure drop in a forward flow direction but may only provide shut-off capabilities for up to a 100 psi pressure drop in a reverse flow direction.
Process fluid control devices may not provide equal shut-off capabilities in both fluid flow directions due to mechanical tolerances in the construction of the process fluid control device and the design of the process fluid control device. In a forward flow direction, a movable flow control member used to control and/or stop fluid flow through the process fluid control device (e.g., a disk of a butterfly valve or any other mechanical element used to control and/or stop fluid flow) may have tapered edges so that the diameter at one end of the movable flow control member is larger than the diameter of the flow control member at an opposite end. The movable flow control member may be coupled to the process fluid control device so that the end of the movable flow control member having the larger diameter is configured to prevent a sealing member from flexing too far the in the forward fluid flow direction. In particular, in response to fluid pressure in the forward flow direction, the increasing diameter of the movable flow control member allows the sealing member to flex and maintain contact with the outer surface (e.g., the tapered edge) of the movable flow control member. In a reverse flow direction, the amount the sealing member flexes in the reverse flow direction may be too large to maintain contact with the tapered edge of the movable flow control member. As a result, a fluid seal between the sealing member and the movable flow control member may be compromised (e.g., broken) and fluid is allowed to pass by the movable flow control member.